Restock-Predictor: AI-Powered Inventory Forecasting for Etsy & Shopify Side Hustles with TabPFN

A developer built Restock-Predictor, an open-source inventory forecasting micro-SaaS for independent Etsy and Shopify sellers that uses the TabPFN prior-data fitted network to perform zero-shot in-context regression on tabular sales data in sub-second inference. The tool extracts temporal features such as day-of-week seasonality, weekend flags, rolling 7-day means and lag-7 anchors, then returns quantile probabilistic forecasts, with MongoDB Atlas audit logging and a Streamlit/Plotly frontend, packaged with a Render deployment blueprint. The developer argues TabPFN avoids the token-arithmetic hallucinations and prompt costs of using standard LLMs for forecasting.

This is a submission for the Hacktoberfest Open-Source AI Challenge Week 2: Side Hustle https://dev.to/challenges/hacktoberfest-week2-2026-10-12 Independent e-commerce creators—especially Etsy artisans, Shopify boutique owners, and print-on-demand side hustlers—routinely suffer from the "Inventory Trap" : Large enterprises solve this with multimillion-dollar ERP systems like SAP or NetSuite, or expensive $300/month demand forecasting SaaS tools. Solopreneurs and side hustlers, on the other hand, are left guessing in Excel sheets or frantically reordering supplies after they've already sold out. Restock-Predictor is an AI-powered inventory intelligence micro-SaaS built specifically for these independent sellers. Store owners simply drag and drop their historical sales export columns: Date , Item ID , Quantity Sold . Within two seconds, the platform: Etsy makers and Shopify side hustlers generating \$2,000 to \$25,000/month in revenue. For an artisan maker, avoiding just one single stockout on a high-margin weekend pays for an entire year of a \$15–\$25/month subscription. SKU-SOY-CANDLE , SKU-CERAMIC-MUG , SKU-LINEN-TOTE . Plus Jakarta Sans , and zero default-Streamlit clutter. +X.X% vs prior 30d , safety stock buffer ratios, and SKU health tracking. A High-Aesthetic Minimum Viable Product MVP for e-commerce side hustles and independent makers Etsy/Shopify , submitted for the DEV.to Hacktoberfest Open-Source AI Challenge. Independent e-commerce makers frequently face the "Inventory Trap" : Traditional time-series forecasting requires extensive statistical tuning ARIMA stationarity, Prophet holidays, or iterative GBDTs like XGBoost . Meanwhile, attempting to use standard LLMs like GPT-4 fails due to token arithmetic hallucinations, linear drift failures, and extreme prompt token costs . Restock-Predictor solves this with a TabPFN Prior-Data Fitted Network foundation model — performing zero-shot in-context regression in sub-second inference. Combined with MongoDB Atlas for audit logging and Streamlit + Plotly styled in an obsidian glassmorphism SaaS theme, store owners can upload… .streamlit/config.toml : Custom dark-mode SaaS palette definitions and server configs. app.py : Streamlit frontend featuring custom glassmorphism CSS, Plotly multi-series charts, tabs, and delta metrics. predictor.py : TabPFN API client tabpfn-client , time-series tabular feature extraction, and quantile probabilistic forecasting. db.py : MongoDB Atlas connection manager with latency timeouts, ping verification, and resilient session auditing. render.yaml : Infrastructure as Code IaC blueprint for one-click deployment on Render. sample data.csv : 270-row baseline dataset modeled with weekend lifts and realistic trends. Instead of forcing a language model to do math, Restock-Predictor is built around TabPFN tabpfn-client , an open-weight foundation model designed purely for tabular data. TabPFN was pre-trained on millions of synthetic tabular datasets to approximate Bayesian inference in a single transformer forward pass. It requires: To feed TabPFN the cleanest tabular signal, we extract structural temporal features from the raw sales timestamps: Extract tabular representations for TabPFN's in-context attention mechanism df "day index" = df "Date" - min date .dt.days Continuous linear drift df "day of week" = df "Date" .dt.dayofweek Weekly seasonality 0=Mon, 6=Sun df "is weekend" = df "day of week" .apply lambda w: 1 if w = 5 else 0 Weekend Etsy spikes df "day of month" = df "Date" .dt.day Payday purchasing patterns df "rolling 7d mean" = df "Quantity Sold" .rolling 7, min periods=1 .mean Current demand baseline df "lag 7" = df "Quantity Sold" .shift 7 .fillna ... Same-day previous week anchor Inventory forecasting isn't just about the average—it's about the risk tail. We query TabPFN for both median expectations and 90th-percentile quantiles : Predict both expected demand median and 90% risk ceiling for safety stock quantiles = model.predict X future, output type="quantiles", quantiles= 0.5, 0.9 expected demand = quantiles :, 0 safety stock ceiling = quantiles :, 1 We established a bespoke aesthetic by pairing .streamlit/config.toml with custom CSS injected via st.markdown : 1px solid rgba 255, 255, 255, 0.08 borders. fill="tonexty" . Every upload triggers a non-blocking insert into MongoDB Atlas via pymongo : log doc = { "timestamp": datetime.now timezone.utc .isoformat , "filename": filename, "row count": total rows, "item count": item count, "items": unique items, "metadata": metadata payload } collection.insert one log doc If network restrictions or unconfigured credentials arise during demo testing, a resilient session fallback catches the exception so the UI never crashes. Configured via render.yaml with automated pip package resolution and Streamlit port binding to Render's dynamic $PORT . Why build with an open-weight tabular foundation model like TabPFN instead of calling a closed-source general LLM like GPT-4 or Claude? Generative LLMs represent numbers as discrete Byte-Pair Encoding BPE tokens. They have no innate understanding of continuous mathematics, often hallucinating sums, failing to extrapolate gradual linear declines, or inventing phantom sales spikes. TabPFN is a specialized transformer trained on synthetic prior mathematical functions, treating numerical values with mathematical continuity. Generating 30 days of multi-item forecasts through an autoregressive text LLM requires generating hundreds of output tokens sequentially, taking 8 to 15 seconds. TabPFN processes the entire feature matrix in a single forward pass in less than 500 milliseconds . Inventory planners cannot rely on deterministic point estimates alone; they need to know the volatility spread to calculate safety stock. Closed LLMs can only provide hand-wavy descriptions "sales might surge on weekends" . TabPFN outputs true mathematical predictive distributions and quantiles. Feeding 90 days of multi-item sales logs into a commercial chat API consumes tens of thousands of tokens per run and exposes confidential boutique business metrics to third-party commercial training pools. TabPFN accepts compact numerical arrays locally or via lightweight API endpoints without token bloat. This entire project was engineered collaboratively with Antigravity , an agentic pair programmer. 0.0.0.0 , dynamic $PORT handling, and disabling CORS/XSRF for Render . To test Restock-Predictor with a real-world side hustle, I shared the live Render deployment with Priya , an independent maker running a hand-poured candle and artisan ceramics shop on Etsy. Priya had been ordering candle wax and ceramic clay in arbitrary batches every two weeks. Last month, a sudden weekend feature on an Etsy curation feed caused her best-selling soy candle to sell out in 36 hours. She missed out on an estimated \$340 in lost sales while waiting 5 days for a new shipment of soy wax flakes. Priya exported her last 90 days of sales as a CSV and uploaded it to Restock-Predictor on Render. "Seeing the amber 'Safety Buffer' band on the chart made it immediately obvious why I keep running out of stock on weekends. My base sales look manageable, but the weekend surge pushes demand way past my typical reorder point. Having an exact restock number with safety buffer included—and being able to download it as a spreadsheet—saved me hours of manual math." Priya asked if future versions could let her input lead times for her suppliers e.g., "supplier takes 6 days to deliver" so the app can alert her on the exact calendar day she needs to submit her order. Restock-Predictor is deployed natively on Render using an Infrastructure as Code blueprint render.yaml https://github.com/sanjana806/Restock-Predictor/blob/main/render.yaml . streamlit run app.py --server.port $PORT --server.address 0.0.0.0 . / stcore/health . MONGO URI and model tokens TABPFN API KEY are managed through Render's environment dashboard sync: false , keeping the public repository fully secure. TabPFN tabpfn-client is the algorithmic core of the platform. We utilize TabPFN's zero-shot in-context learning to perform tabular regression across engineered time-series features without hyperparameter tuning, and extract probabilistic 90th-percentile quantiles to calculate inventory safety stocks. All upload batches, row counts, unique catalog SKUs, and processing metadata are immutably logged to a MongoDB Atlas cluster pymongo . A dedicated audit tab in the dashboard provides store owners with transparent traceability over past inventory analysis runs.